Properties of RF sputtered tetragonal and hexagonal barium titanate films

Some physical properties of tetragonal and hexagonal barium titanate films are reported. The as-grown films were amorphous, and annealing at 700°C resulted in crystallization of the films. The amorphous films deposited from the hexagonal phase target (h-a:BaTiO₃) had higher refractive index values than those sputtered from a tetragonal phase target (t-a:BaTiO₃). The h-a:BaTiO₃ films had lower bandgap values than the t-a:BaTiO ₃ films. Crystallization altered the bandgap values in the case of tetragonal films, whereas no change was observed in hexagonal films. The measured DC conductivity showed a slight decrease on crystallization in both the phases, and the tetragonal films had a ferroelectric-to-paraelectric transition, while the hexagonal films did not show any indication of phase transition in the measured temperature region